Method of flock printing utilizing as an adhesive a solvent solution of a copolymer of acrylonitrile, alkyl ester, and a crosslinking comonomer and flocked fabric



United States Patent 3,336,149 METHOD OF FLOCK PRINTING UTILIZING AS ANADHESIVE A SOLVENT SOLUTION OF A COPOLYMER 0F ACRYLONITRILE, ALKYLESTER, AND A CROSSLINKING COMONO- MER AND-FLOCKED FABRIC Leonard J. Fox,Berkeley Heights, Henry Stanley, Newark, and Samuel Gold, BerkeleyHeights, N.J., assignors to National Starch and Chemical Corporation,New York, N.Y., a corporation of Delaware No Drawing. Filed Sept. 25,1963, Ser. No. 311,322 3 Claims. (Cl. 117-25) This invention relates tothe preparation of flocked articles, and more particularly, to theadhesive compositions utilized in preparing such flocked articles.

Flock printing processes are commonly employed for the preparation offabrics which are used in the manufacture of hats, shoes, dresses,ribbons, rugs, carpets, and similar articles. In these flock printingmethods, short fibers are deposited on a fabric, usually in a definitepattern, and are held fast to the fabric by means of a suitableadhesive. The variety of attractive patterns, as well as the soft handor touch, obtained through flock printing makes this technique an idealmeans of preparing decorative fabrics.

The success of flock printing techniques is, to a great extent,dependent upon the adhesives used therein to ad here the flock fibers tothe fabric. Adhesives formerly used for flock printing have exhibited anumber of shortcomings. Thus, for example, plasticized nitrocelluloselacquers, which have been used as flock binders, have low flash points,thereby making them hazardous to work with and unsuitable for use ongarments. Rubber cements have also been proposed as binders, but suchcements impart poor color to fabrics and require lengthy curing cycles.In addition, rubber cements are often sensitive to dry cleaningsolvents. Various other materials which have been employed as flockprinting binders have generally proved unsatisfactory with respect totheir sensitivity to washing, dry cleaning, and abrasion.

It is an object of this invention to prepared adhesive compositions forflock printing, said adhesive compositions having extremely high wash,dry clean, and abrasion resistance. Another object of this invention isto prepare flock printing adhesive compositions which require minimalcuring cycles. A further object of this invention is the preparation offlocked fabrics which possess a soft hand or feel. Other objects and theadvantages of this invention will be apparent from the discussion thatappears hereinafter.

In accordance with the invention, copolymers of alkyl esters of acrylicacid with certain comonomers, hereinafter defined, are advantageouslyused as flock binders in flock printing methods. The use of these bindersystems in the flock printing process imparts soft hand, along withoutstanding wash, abrasion, and dry clean resistance to the resultingfabrics. Our novel flock printing adhesives are particularly noteworthyin that they impart abrasion resistance, not only to dry patterns, butalso to patterns wet with water or organic solvents. A furtherinteresting property of these copolymers is their ability to cure atroom temperature. It should be noted that in connection with adhesivesfor flock printing, the terms adhesives and binders are usedinterchangeably, and are synonymous.

The copolymers which are used in preparing the flock printing adhesivesof this invention should contain from 55 to by weight, of an alkyl esterof acrylic acid wherein said alkyl group may contain from 1 to 8 carbonatoms; from 5 to 40%, by weight, of acrylonitrile; and, from 0.5 to10.0%, by weight, of a crosslinking comonomer, the total, of course,being Of particular utility as the aforementioned crosslinkingcomonomer, there may be listed N-methylol acrylamide, N-methylolmethacrylamide, glycidyl acrylate, glycidyl methacrylate, and the like.

The copolymers which comprise the base for our novel flock printingbinders may be prepared by any suitable polymerization method. Usuallythe polymerization is carried out in an organic solvent medium byheating the mixture of comonomers at the reflux temperature of thesolvent, thus insuring a constant temperature and dissipation of theheat of reaction in evaporating the solvent. Solvent soluble freeradical initiating catalysts of the peroxide or azo type are utilized inthese polymerizations. If the resulting polymer is insoluble in thesolvent, it can be filtered, washed, and thereafter dissolved in asolvent in which it is soluble. The copolymers can be utilized in theform of the lacquers wherein they were prepared, or these lacquers, inturn, may be converted to aqueous emulsions prior to their use in theflock printing process. Thus, lacquers of these copolymers may bereadily emulsified by adding an aqueous solution of an emulsifier, suchas polyvinyl alcohol, morpholine-oleic acid mixtures, and the like, tothe lacquer while the lacquer is being vigorously agitated. The organicsolvent is then removed from the mixture by flash distillation or anyother suitable method. The polymerization may also be carried out bydispersing the comonomers as fine droplets in a large volume of waterthrough the use of emulsifying agents. Then the polymerization iseffected in the presence of water soluble catalysts, such as, forexample, the persulfates. At any rate, the total solids content of theformulations may range from about 30% to about 65%, by weight.

It should be noted that neither the copolymers described herein nor themethods whereby they are prepared constitute the novel aspect of thisinvention. Rather, it is the use of said copolymers in flock printingand the surprisingly advantageous results of such use which comprise theparticular concept of this invention.

In addition to the copolymers described previously, the flock printingadhesives of this invention may also include such other ingredients asinert fillers, pigments, catalytic agents, antioxidants, ultra violetstabilizers, diluents, thermosetting resins, plasticizers, and anysimilar additive with which the practitioner may wish to modify theproperties of the formulation.

The adhesive formulations used in the process of this invention areapplicable to any of the conventional flock printing techniques. Inthese techniques, the adhesive formulation is ordinarily deposited byany suitable means onto the surface of a fabric substrate which iscarried on a moving belt or roll. The adhesive is usually applied to thefabric by means of a spray gun, perforated screens, or engraved rollersso as to form, if desired, a definite pattern or design. Thereafter, anexcess of fiber flock is deposited onto the adhesive coated fabric andthe fabric is then carried to a drying oven wherein the drying or curingof the adhesive is effected. After curing, the fabric is run through abrushing and vacuum machine which serves to remove the loose fibers thatare not part of the desired pattern.

As was mentioned previously, the copolymers used in our flock printingprocess may be applied either as lacquers or as aqueous emulsions. Theseadhesives are usually applied in a wet coating thickness of from about 1mil to about 25 mils. In addition, the adhesive compositions used; inthis invention are readily adaptable to both vibration and electrostaticmethods of flock printing.

The drying cycles employed to cure the adhesive coated fabric may bevaried according to the particular needs of the practitioner. Optimumresults are obtained by exposing the flocked fabric to temperatures ofabout 300 F. for from 3 to minutes. Despite this relatively short curingtime, flocked fabrics embodying our adhesives nevertheless attainextremely high wash and solvent resistant properties. A comparabledegree of wash and solvent resistance could be achieved by adhesivesheretofore utilized only by maintaining higher temperatures forconsiderably longer periods of time. Furthermore, the adhesivecompositions used in this invention possess the particular advantagethat they can be cured at room temperature in about 30 minutes, withoutany heating cycle. However, in order to effect room temperature curing,it is desirable to add to the formulation approximately 0.25%, by weightof the copolymer solids, of a suitable catalyst. Such catalysts includearyl sulfonic acids, alkyl sulfonic acids, aryl phosphonic acids, alkylphosphonic acids, trihalo acetic acids, poly nitrobenzoic acids, polynitrophenols, alkyl esters of aryl sulfonic acids, mineral acids, alkylesters of sulfuric acid, and similar compounds. These catalysts may alsobe included, if desired, in those compositions of our invention whichare to be cured at elevated temperatures.

The flock fibers used in the process of this invention may be selectedfrom any natural or synthetic fibers or any combination of natural andsynthetic fibers. These fibers can be such natural fibers as cotton,wool, silk, and the like, or such synthetic fibers as rayon, polyamide,polyester, acetate, acrylic, and the like. The length and diameter ofthe fibers which are used are not critical to the invention. The deniersof the fibers may be varied along with the lengths, and various texturesof different types of flock fibers may be blended.

It can be seen, therefore, that the adhesive compositions of thisinvention imbue the flock printing process with a number of significantadvantages. Thus, these adhesives show high wash, dry clean, andabrasion resistance without sacrificing the soft hand which is necessaryfor commercial acceptability. Also of obvious commercial importance isthe ability of these adhesives to cure very rapidly at elevatedtemperatures, or even at room temperature if so desired.

In the following examples, which further illustrate the embodiment ofthis invention, all parts given are by weight, unless otherwiseindicated.

Example I This example illustrates the preparation of the adhesivecompositions of this invention and their subsequent use in a flockprinting process.

In this example and in the examples that follow, the same procedureswere utilized to test the wash, dry clean, and abrasion characteristicsof the flocked fabrics.

In testing wash resistance, the flocked and cured fabric was subjectedto an ordinary washing in a typical household washing machine. Anychange in hand or loss of flocked fibers was considered detrimental.

In testing dry clean resistance, the flocked and cured fabric was placedin a container filled with perchloroethylone (a dry cleaning solvent)and steel balls and was then tumbled at 170 F. for 15 minutes. Anychange in hand or loss of flocked fibers was considered detrimental.

In testing solvent abrasion resistance, the flocked and cured fabric wassoaked in perchloroethylene and abraded by rubbing the surface of thefabric with the fingernail. Any loss of flocked fibers due to theabrasion was considered detrimental.

4 (a) A reaction vessel fitted with a water-cooled condenser, stirrerand gas inlet tube was charged with a mixture of the followingingredients:

5 Component: Parts Acrylonitrile 125 Butyl acrylate 37.5 Toluene 213Methyl alcohol 61 N-methylol acrylamide (40% solids in isopropylalcohol) Isopropyl alcohol 51 Benzoyl peroxide 3.75

The mixture was then heated, with stirring, to about 167 F. while astream of nitrogen was slowly bubbled through the solution. Heating wascontinued for 9 hours whereupon the reaction mixture was cooled anddischarged from the reaction vessel.

The copolymer lacquer thus prepared was deposited upon a fabricsubstrate carried on a conveyor blanket, in a wet coat thickness of 15mils. Rayon fibers 0.05 inch in length and 1.5 denier in diameter werethen flocked upon the wet adhesive layer with constant agitation due tothe action of beater bars upon the conveyor blanket. The wet flockedfabric was then passed into a hot air oven wherein it was heated at atemperature of 300 F. for about 5 minutes. The resulting flocked fabric,when subjected to the tests heretofore described, exhibited propertiesof wash, dry clean, and abrasion resistance which were superior to theproperties exhibited by flocked fabrics employing conventional flockingadhesives.

(b) An aqueous emulsion having the following composition:

Component:

Acryonitrile 25 Butyl acrylate 75 N-methylol acrylamide 4 Ammoniumpersulfate 0.15 Sodium acetate 0.15 Polyvinyl alcohol 4.5 Water 90 Partswas prepared as follows:

A reaction vessel fitted with a water-cooled condenser, stirrer, and gasinlet tube was charged with the water, ammonium persulfate, sodiumacetate, polyvinyl alcohol, and about one-third of the acrylonitrile,butyl acrylate, and N-methylol acrylamide. This mixture was heated, withstirring, to about 167 F. while a stream of nitrogen was slowly bubbledthrough the solution. When the temperature of the mixture had reached167 F., the remaining two-thirds of the acrylonitrile, butyl acrylate,and N- methylol acrylamide was added uniformly thereto over a 3-hourperiod. After all of the monomers had been added, the mixture was heatedto a temperature of 203 F. and maintained at this temperature for about15 minutes, at the end of which time the mixture was allowed to cool toroom temperature and discharged from the reaction vessel.

The copolymer emulsion thus prepared was deposited upon a fabricsubstrate carried on a conveyor blanket in a wet coat thickness of 15mils. Rayon fibers 0.05 inch in length and 1.5 denier in diameter werethen flocked upon the wet adhesive layer with constant agitation due tothe action of beater bars upon the conveyor blanket. The wet flockedsurface was then passed into a hot air oven where- 7 in it was heated ata temperature of 300 F. for about 5 minutes. The resulting flockedfabric, when subjected to the tests heretofore described, exhibitedproperties of wash, dry clean, and abrasion resistance which weresuperior to the properties exhibited by flocked fabrics employingconventional flocking adhesives.

Example II This example further illustrates the preparation of theadhesive compositions of this invention.

The general procedure described in Example I was employed to prepare thecompositions presented in the table below.

Formulation Number Components Acrylonitrile 5 40 14. 5 14. 5 25 25 Butylacrylate 90 55 85 75. 5 Methyl acryla 2-ethyl hexylacrylate. 75 70 70 7OGlycidyl acrylat 5 Glycidyl methaerylate 5 N -methylol acrylamide 5 5 0.5 l0 5 5 5 N -methylol methacryl mid P 5 Benzoyl peroxide- 0. 75 O. 750. 75 0.75 0. 75 .0. 75 0. 75 0.75 0. 75 0. 75 O. 75 Isopropyl alcohol.22 22 22 22 22 22 22 22 22 22 22 Meth alcohol 18 18 18 18 18 18 18 18 1818 18 Toluene 60 60 60 60 60 60 60 60 60 60 60 Para-toluenesulfonlc acid0. 25 0. 25 0. 25

utilized are especially characterized by flexibility and soft hand. Theadhesive compositions of this invention also are commerciallysignificant in that they can be cured very rapidly at elevatedtemperatures or even at room temperature if so desired.

Any departure from the above description which conforms to thisinvention is intended to be included within the scope of the inventionas defined by the following claims.

We claim:

1. In the method of flock printing which comprises applying an adhesivecomposition to a substrate, depositing fibers on said adhesive coatedsubstrate, curing said adhesive coated substrate, and thereafterremoving excess fibers, the improvement which comprises employing as theadhesive composition therein an organic solvent solution of a copolymerconsisting of from 5 to by weight, of acrylonitrile, from 0.5 to 10%, byweight, of a crosslinking comonomer selected from the group consistingof glycidyl acrylate and glycidyl methacrylate, and from 55 to 90%, byweight, of an alkyl ester of acrylic acid wherein said alkyl groupcontains from 1 to 8 carbon atoms; said organic solvent solution beingentirely devoid of any other polymeric ingredients.

weight, of an organic solvent solution of a copolymer consisting of from5 to 40%, by Weight, of acrylonitrile, from 0.5 to 10%, by weight, of acrosslinking comonomer selected from the group consisting of glycidylacrylate and glycidyl methacrylate, and from 55 to by weight, of analkyl ester of acrylic acid wherein said alkyl group contains from 1 to8 carbon atoms; said organic solvent solution being entirely devoid ofany other polymeric ingredients.

3. A flocked fabric comprising a substrate fabric to which flock fibersare adhesively bonded with the dried residue of an organic solventsolution of a copolymer consisting of from 5 to 40%, by weight, ofacrylonitrile, from 0.5 to 10%, by weight, of a crosslinking comonomerselected from the group consisting of glycidyl acrylate and glycidylmethacrylate, and from 55 to 90%, by weight, of an alkyl ester ofacrylic acid wherein said alkyl group contains from 1 to 8 carbon atoms;said organic solvent solution being entirely devoid of any otherpolymeric ingredients.

References Cited UNITED STATES PATENTS 2,310,965 2/ 1943 Leavy et al117-25 2,881,087 4/ 1959 Schwartz et a1. 117-25 X 2,976,167 3/1961Maeder et al. 117-33 2,994,676 8/ 1961 Kucsan et a1 260-805 3,099,514 7/1963 Haber 117-33 X 3,117,108 1/1964 Calvete 260-805 3,231,533 1/1966Garrett et a1 260-29.6

WILLIAM D. MARTIN, Primary Examiner. MURRAY TILLMAN, Examiner.

J. ZIEGLER, W. D. HERRICK, Assistant Examiners.

1. IN THE METHOD OF FLOCK PRINTING WHICH COMPRISES APPLYING AN ADHESIVECOMPOSITION TO A SUBSTRATE, DEPOSITING FIBERS ON SAID ADHESIVE COATEDSUBSTRATE, CURING SAID ADHESIVE COATED SUBSTRATE, AND THEREAFTERREMOVING EXCESS FIBERS, THE IMPROVEMENT WHICH COMPRISES EMPLOYING AS THEADHESIVE COMPOSITION THEREIN AN ORGANIC SOLVENT SOLUTION OF A COPOLYMERCONSISTING OF FROM 5 TO 40%, BY WEIGHT, OF ACRYLONITRILE, FROM 0.5 TO10%, BY WEIGHT, OF A CROSSLINKING COMONOMER SELECTED FROM THE GROUPCONSISTING OF GLYCIDYL ACRYLATE AND GLYCIDYL METHACRYLATE, AND FROM 55TO 90%, BY WEIGHT, OF AN ALKYL ESTER OF ACRYLIC ACID WHEREIN SAID ALKYLGROUP CONTAINS FROM 1 TO 8 CARBON ATOMS; SAID ORGANIC SOLVENT SOLUTIONBEING ENTIRELY DEVOID OF ANY OTHER POLYMERIC INGREDIENTS.